Terahertz light‐emitting graphene‐channel transistor toward single‐mode lasing

A distributed feedback dual‐gate graphene‐channel field‐effect transistor (DFB‐DG‐GFET) was fabricated as a current‐injection terahertz (THz) light‐emitting laser transistor. We observed a broadband emission in a 1–7.6‐THz range with a maximum radiation power of ~10 μW as well as a single‐mode emission at 5.2 THz with a radiation power of ~0.1 μW both at 100 K when the carrier injection stays between the lower cutoff and upper cutoff threshold levels. The device also exhibited peculiar nonlinear threshold‐like behavior with respect to the current‐injection level. The LED‐like broadband emission is interpreted as an amplified spontaneous THz emission being transcended to a single‐mode lasing. Design constraints on waveguide structures for better THz photon field confinement with higher gain overlapping as well as DFB cavity structures with higher Q factors are also addressed towards intense, single‐mode continuous wave THz lasing at room temperature.